KR102129869B1 - Method for depositing a conductive coating on a surface - Google Patents

Abstract

Provided is a method of depositing a conductive coating layer on a surface, the method comprising depositing fullerene on the surface to produce a treated surface and depositing a conductive coating layer on the treated surface. The conductive coating layer generally contains magnesium. Products produced according to the above method and organic optoelectronic devices are also provided.

Description

Method of depositing a conductive coating layer on the surface{METHOD FOR DEPOSITING A CONDUCTIVE COATING ON A SURFACE}

Cross reference to prior applications

This application claims priority to U.S. Application No. 61/723,127 filed on November 6, 2012 under the Paris Convention, the entire contents of which are incorporated herein by reference.

Technical field

The following relates to electronic devices, and more particularly to methods of manufacturing organic optoelectronic devices. In particular, the following relates to a method of depositing a conductive coating layer comprising magnesium on a surface.

Organic light emitting diodes (OLEDs) typically include a number of organic material layers interposed between conductive thin film electrodes, wherein at least one of the organic layers is an electroluminescent layer. When a voltage is applied to the electrode, holes and electrons are injected from the anode and the cathode, respectively. Holes and electrons injected by the electrode travel through the organic layer to reach the electroluminescent layer. When holes and electrons are very close, they attract each other due to the Coulomb force. The holes and electrons can then combine to form a combined state called exciton. As is well known, excitons decay through radiation recombination, where photons are emitted. On the one hand, excitons may decay through a non-radiative recombination process, at which time photons are not emitted.

The radiation recombination process can occur as a fluorescence or phosphorescence process, depending on the spin state of the electron-hole pair (ie exciton). Specifically, the exciton formed by the electron-hole pair can be characterized as having a singlet spin or triplet spin state. In general, the radioactive decay of singlet excitons produces fluorescence, whereas the radioactive decay of triplet excitons produces phosphorescence.

Approximately one quarter of the excitons formed from organic materials typically used in OLEDs are singlet excitons and the other three quarters are triplet excitons. As is well known, a direct transition from a triplet state to a singlet state is considered a "forbidden" transition in quantum mechanics, and as above, the probability of radiation collapse from triplet state to singlet state is generally very small. Unfortunately, the ground state of most organic materials used in OLEDs is a singlet state, which prevents efficient radiation collapse of excitons at ambient temperature from the triplet state to the singlet ground state at ambient temperature. As above, in a typical OLED, electroluminescence is mainly achieved by fluorescence, thus producing a maximum internal quantum efficiency of about 25%. Note that, as used in the present invention, internal quantum efficiency (IQE) will be understood to be the ratio of all electron-hole pairs occurring in the device that decay through a radiation recombination process.

Radiation decay from the triplet state to the ground singlet state occurs at a very slow rate in most organic materials, but the rate of decay (ie recombination rate) can be significantly increased by introducing species with high spin-orbit binding constant Can. For example, complexes of transition elements, such as Ir(III) and Pt(III), promote the more efficient radiant decay of the high spin-orbit binding constants of these species from triplet to ground singlet. Therefore, it has been used in so-called phosphorescent OLEDs. As above, some or all of approximately 75% of the triplet state excitons can also efficiently transition to singlet ground state and emit light, thus creating a device with a maximum IQE close to 100%. .

The external quantum efficiency (EQE) of an OLED device can be defined as the ratio of the charge carriers provided to the OLED to the number of photons emitted by the device. For example, an EQE of 100% suggests that one photon is emitted for each electron injected into the device. As will be appreciated, the device's EQE is generally substantially lower than the device's IQE. The difference between the EQE and the IQE can generally be attributed to absorption and reflection of light caused by a number of factors, for example various elements of the device. One way to increase the EQE of a device is to use a cathode material with a relatively low work function, so that electrons are easily injected into adjacent organic layers while the device is operating. Typically, aluminum is used as the cathode material due to its advantageous electrical and optical properties. Specifically, it has a work function of 4.1 eV, is an excellent conductor, and has a relatively high reflectance in the visible spectrum when deposited as a film. Moreover, aluminum has advantageous processing properties over some other metals. For example, aluminum has a deposition temperature of approximately 1600 °C.

Aluminum is typically selected as the cathode material, but in some applications, magnesium may, on the one hand, be a cathode material that is more advantageous than aluminum. Magnesium has a lower work function of 3.6 eV compared to aluminum. Magnesium can also be thermally deposited, for example, at a deposition temperature of 400° C. or lower substantially lower than the deposition temperature of aluminum, and thus is more cost effective and easier to process.

However, as shown in U.S. Patent Nos. 4,885,211 and 5,059,862, substantially pure magnesium could not be used as an effective cathode for organic optoelectronic devices because of its poor adhesion to organic materials and low environmental stability. U.S. Publication No. 2012/0313099 further discloses poor adhesion of magnesium to organic surfaces. In addition, magnesium tends to oxidize, and as described above, a device having a magnesium cathode is difficult to manufacture and operate in an oxygen and/or humidity environment because the conductivity of the cathode rapidly decreases with magnesium oxidation.

It is possible to deposit magnesium on various inorganic substrates, such as glass and silicon substrates, but the adhesion coefficient of magnesium on these surfaces is also relatively low, so typical deposition processes known in the art are generally not cost-effective.

In U.S. Pat. An organic electroluminescent device comprising a layer is provided, wherein the adhesion-promoting layer comprises one or more metals or metal compounds. However, at least some of the metals or metal compounds proposed for use as an adhesion-promoting layer by Lyao et al. may be unstable and therefore may not be suitable for long-term use in many applications. For example, metals such as cesium are known to be strong reducing agents, and as above, the metals oxidize rapidly when exposed to water, humidity or air. Therefore, the deposition of such metals is often complex and difficult to integrate into the conventional manufacturing process of organic optoelectronic devices.

In addition, it was previously reported that magnesium selectively attaches to some photochromic molecules in a colored state [JACS 130, 10740 (2008)]. However, the application of the above discovery with respect to organic optoelectronic devices is rare, since the materials are not typically used in organic optoelectronic devices.

As above, there is still a need for a method of promoting adhesion of magnesium to a surface, alleviating one or more of the defects known in the art.

In one aspect, a method of depositing a conductive coating layer on a surface is provided. The method comprises depositing fullerene on the surface to produce a treated surface, depositing a conductive coating layer on the treated surface, the conductive coating layer comprising magnesium.

In another aspect, there is provided a product comprising a substrate having a surface coated with a conductive coating layer, the conductive coating layer comprising magnesium, and fullerene disposed at an interface between the conductive coating layer and the surface.

In yet another aspect, an organic optoelectronic device is provided, the organic optoelectronic device comprising an anode and a cathode (the cathode includes magnesium), an organic semiconductor layer interposed between the anode and the cathode, and the organic semiconductor layer And a fullerene disposed between the cathode.

A similar OLED device comprising a magnesium cathode according to the present invention is expected to provide substantially longer shelf life compared to the same device comprising a conventional aluminum cathode, especially when properly encapsulated.

Embodiments will now be described with reference to the accompanying drawings as examples only, in the drawings:
1 is a diagram illustrating a method of depositing a conductive coating layer according to one embodiment, wherein separate magnesium and fullerene sources are used;
2 is a diagram illustrating a method of depositing a conductive coating layer according to one embodiment, wherein a common deposition source comprising magnesium and fullerene is used;
3A is a diagram of a magnesium film deposited on an inner-monolayer fullerene adhesion promoting layer according to one embodiment;
3B is a diagram of a magnesium film deposited over a fullerene adhesion promoting layer according to one embodiment;
3C is a diagram of a co-deposited conductive coating layer comprising magnesium mixed with fullerene according to one embodiment;
4 is a diagram illustrating a shadow mask deposition process for selectively depositing fullerene on a substrate surface in one embodiment;
5A-5C are diagrams illustrating a micro-contact printing process for selectively depositing fullerene on a substrate surface according to one embodiment;
6 is a diagram illustrating a process for depositing magnesium on a fullerene-treated surface of a substrate according to one embodiment;
7 is a diagram illustrating a shadow mask deposition process, wherein the shadow mask is treated with an organic coating layer to reduce the adhesion of magnesium to the shadow mask;
8 is a diagram illustrating a shadow mask deposition process without treating the shadow mask with an organic coating layer;
9 is a diagram illustrating a shadow mask deposition process in which the shadow mask is treated with an organic coating in one embodiment;
10 is a device structure diagram of an exemplary red phosphorescent organic light emitting diode (OLED);
FIG. 11 is a plot showing the relationship between current density and voltage of the first OLED device of FIG. 10 comprising a magnesium cathode and the second OLED device of FIG. 10 comprising an aluminum cathode;
12 is a chart showing the relationship between the standardized electroluminescence intensity and wavelength of two OLED devices, the first device comprising a magnesium cathode and the second device an aluminum cathode;
13 is a chart showing the relationship between the external quantum efficiency (EQE) and luminance for two OLED devices, the first device comprising a magnesium cathode and the second device an aluminum cathode;
14 is a chart showing the relationship between reflectance and wavelength for magnesium and aluminum thin films deposited on glass;
15 is a chart showing the relationship between extinction coefficient and wavelength for buckminster fullerene;
16 is a chart showing the relationship between current density and voltage for an OLED device comprising a magnesium cathode deposited over a fullerene layer of various thickness;
17 is a chart showing the relationship between EQE and fullerene adhesion promoting layer thickness for an OLED device comprising a magnesium cathode;
18 shows the current density and current density for an OLED device comprising one of a magnesium cathode deposited using a shadow mask, an aluminum cathode deposited using a shadow mask, and optionally a magnesium cathode deposited on a treated surface. It is a chart showing the relationship between voltages;
19 is a chart showing the relationship between power efficiency and luminance for an OLED device comprising a magnesium-fullerene cathode in which various concentrations of fullerene are present;
20 is a chart showing the decay rate of luminance of an OLED device including various cathode structures;
21 is a chart showing the relationship between current efficiency and luminance for an OLED device comprising a C ₆₀ adhesion promoting layer or a C ₇₀ adhesion promoting layer;
22 is a chart showing the photoelectric strength as a function of the binding energy for the fullerene film, the magnesium film deposited on the fullerene adhesion promoting layer, and the magnesium film mixed with fullerene;
23A is an optical micrograph of an exemplary OLED device comprising an aluminum cathode, immediately after manufacturing;
23B is an optical micrograph of the exemplary OLED device of FIG. 23A including an aluminum cathode, taken after the device has been exposed to ambient conditions for 208 hours;
24A is an optical micrograph of an exemplary OLED device comprising magnesium cathode deposited on a fullerene adhesion promoting layer immediately after manufacture;
24B is an optical micrograph of the exemplary OLED device of FIG. 24A including magnesium cathode, taken after the device has been exposed to ambient conditions for 208 hours;
25 is a chart showing cracks in OLED devices developed with dark spots over time for the exemplary OLED devices of FIGS. 23A and 24A.

For simplicity and clarity of illustration, where deemed appropriate, drawing numbers may be repeated between figures to indicate corresponding or similar elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the exemplary embodiments disclosed herein. However, those skilled in the art will appreciate that the exemplary embodiments disclosed herein can be practiced without these specific details. In other instances, well-known methods, procedures and ingredients have not been described in detail so as not to obscure the exemplary embodiments disclosed herein.

In one aspect, a method is provided for depositing a conductive coating layer on a surface, the method treating the surface by depositing fullerene on the surface to produce a treated surface, and a conductive coating layer on the treated surface And depositing, the conductive coating layer includes magnesium.

Although the following is described with reference to the deposition of a conductive coating layer comprising magnesium, it will be appreciated that the principles outlined in the invention can be applied to other metals, especially alkaline earth metals. For example, the deposited material can include beryllium, calcium, strontium or barium, mixtures of various metals, or mixtures or compounds comprising one or more metals and fullerenes. However, for clarity of illustration, we provide an example with reference to magnesium, which is a minimally reactive alkaline earth metal and may be a desirable candidate for applications involving deposition on organic surfaces, for example in the fabrication of OLED devices.

Based on previous discovery and experimental observations, the inventors assume that fullerenes act as nucleation sites for the deposition of a conductive layer comprising magnesium, as further described in the present invention. For example, when a magnesium or magnesium alloy is deposited on a fullerene-treated surface using an evaporation process, the fullerene molecule acts as a nucleation site for initiating condensation (ie de-sublimation) of the magnesium or magnesium alloy. . It has also been observed that in some cases less than a single layer of fullerene may be provided on the treated surface to act as a nucleation site for successful deposition of magnesium. As will be appreciated, treating the surface by depositing multiple fullerene monolayers can result in a greater number of nucleation sites.

However, it will be appreciated that the amount of fullerene deposited on the surface can be above or below one monolayer. For example, the surface can be treated by depositing 0.1 monolayers, 1 monolayer, 10 monolayers, or more fullerenes. As used in the present invention, depositing a single layer of fullerene means that the amount of fullerene deposited on the surface is equivalent to the amount of fullerene required to cover the desired area of the surface with a single layer of fullerene molecules. Will understand. Similarly, as used in the present invention, depositing 0.1 monolayer fullerenes requires that the amount of fullerenes deposited on the surface is required to cover 10% of the desired area of the surface with a single layer of fullerene molecules. You will understand that it means equal to the amount of. For example, due to the lamination of fullerene molecules, depositing a single monolayer of fullerene on a surface may not cover some areas of the surface, while other areas of the surface may deposit more than two layers of fullerene. Will know.

Turning now to FIG. 1, magnesium and fullerene are deposited on the surface of the substrate 100 using a magnesium source 102 and a fullerene source 104, respectively. It will be appreciated that various systems and devices that can be used for the deposition of these materials are well known in the art.

In one embodiment, fullerene is deposited on the surface of the substrate 100 by initiating deposition by the fullerene source 104 prior to initiating deposition by the magnesium source 102. In the above embodiment, the surface of the substrate 100 is processed by deposition of fullerene so that a fullerene adhesion promoting layer is formed on the surface of the substrate 100.

As mentioned above, the fullerene adhesion promoting layer may not completely cover the surface of the substrate 100, whereby a significant portion of the surface of the substrate 100 may remain uncovered. On the other hand, the surface of the substrate 100 may be completely covered with fullerene. Once the surface of the substrate 100 has been treated, magnesium may be deposited by the magnesium source 102 to form a conductive coating layer. Fullerene deposited on the surface of the substrate 100 may act as a nucleation site, which causes the magnesium to bind to the fullerene molecule and subsequently grow the magnesium through further deposition of magnesium to form a conductive coating layer. I can do it. It is further assumed that spaces or gaps between the fullerene molecules on the treated surface are gradually filled with magnesium as magnesium is deposited by the magnesium source 102.

In one embodiment, the fullerene source 104 may continue to deposit fullerene molecules on the surface of the substrate 100 while magnesium is deposited for the magnesium source 102, whereby the deposition It is possible to create a conductive coating layer in which fullerene molecules are dispersed through the entire magnesium or inside the magnesium. On the other hand, in another embodiment, the fullerene source 104 may stop the deposition of fullerene molecules on the surface if the surface has been treated by deposition of a fullerene adhesion promoting layer. In this way, the resulting conductive coating layer will comprise a substantially pure magnesium or magnesium alloy coating layer.

It will be appreciated that the magnesium source 102 may initiate deposition of magnesium prior to or simultaneously with the fullerene source 104. However, in such a case, it is unlikely that most of the magnesium incident on the surface before the surface of the substrate 100 is processed by deposition of fullerene will not adhere to the surface. As above, the conductive coating layer will only start to form if the surface is treated with a fullerene adhesion promoting layer. Moreover, if a magnesium coating layer is to be formed, there will be little if not fullerene species at the interface between the magnesium coating layer and the surface on which the magnesium is deposited.

In one embodiment, the fullerene and/or the magnesium are deposited using an evaporation process. As will be understood, the evaporation process is a type of physical vapor deposition (PVD) process wherein one or more source materials are evaporated or sublimed under a vacuum environment and deposited on the target surface through condensation of the one or more evaporated source materials. do. It will be appreciated that a variety of different evaporation sources can be used to heat the source material and, as above, the source material can be heated in a variety of ways. For example, the source material can be heated by electric filament, electron beam, induction heating, or resistance heating.

As an example, the deposition conditions for C ₆₀ can be approximately 430-500° C. at a pressure of 10 ⁻⁷ Torr, thereby producing a deposition rate of about 0.1 Angstroms per second. The deposition conditions for magnesium can be approximately 380-430° C. in a Knudsen cell at a pressure of approximately 10 ⁻⁷ Torr, thereby producing a deposition rate of at least about 2 Angstroms per second. However, it will be appreciated that other deposition conditions can also be used.

For example, magnesium can be deposited at temperatures below 600° C. to achieve faster deposition rates, eg, 10-30 nm or more per second. Regarding Table 1 below, various deposition rates measured using K-cell magnesium deposition sources are provided to deposit substantially pure magnesium on a fullerene-treated organic surface of approximately 1 nm. Various other factors, such as, but not limited to, the distance between the source and the substrate, the properties of the substrate, fullerene coverage on the substrate, the type of source used and the shape of the material flow from the source also affect the deposition rate. You know you can go crazy. Subsequently, substrates 1 to 4 were used to fabricate the OLED device according to the method disclosed below.

Magnesium deposition rate with temperature Board Temperature (℃) Speed (angstrom/s) One 510 10 2 525 40 3 575 140 4 600 160

Those skilled in the art will appreciate that the specific processing conditions used may vary and may vary depending on the equipment used to effect the deposition. In addition, it will be appreciated that higher deposition rates are generally obtained at higher temperatures, but certain deposition conditions can be selected by those skilled in the art, for example, by placement of a substrate closer to the deposition source.

In one embodiment, both the magnesium and fullerene may be deposited using the same deposition source. 2, the surface of the substrate 100 subjected to a co-deposition process is illustrated, wherein a common deposition source 202 deposits a material containing magnesium and fullerene to treat the surface and deposit a conductive coating layer Order. Both magnesium and buckminsterfullerene (C ₆₀ ) are known to have similar sublimation temperatures (about 400° C.) under high vacuum conditions (eg, pressures below about 10 ⁻¹ Torr). As above, both magnesium and C ₆₀ can be deposited using a deposition process from a single common source material formed by mixing the Mg and C ₆₀ source materials.

The process disclosed above and illustrated in FIG. 1 allows fullerene to be deposited simultaneously with magnesium, but by providing a common deposition source for evaporating common source materials, the resulting conductive coating layer can be more uniform and the complexity of the deposition process It is noted that it can be reduced. The common deposition source 202 may also be molded to match the substrate. For example, the magnesium and fullerene co-deposition sources can be shaped into a V shape so that a large area of the substrate can be covered with the conductive film. It will be appreciated that the relative amounts of fullerene and magnesium in the common source 202 can vary. For example, the common source may include 1% by weight fullerene, 5% by weight fullerene, or 10% by weight fullerene, the rest being magnesium alloy or substantially pure magnesium.

In one example, common source materials for use with the common deposition source 202 include magnesium and fullerene. Moreover, the common source material may be in solid form, for example in rods, powders, or pellets. The common source material may also be in the form of granules. The solid common source material can be formed by pressing and/or heating a mixture of magnesium and fullerene. The resulting common source material may contain magnesium fulleride species. However, various other methods can be used to form a solid common deposition source to simplify distribution and reduce the exposed surface area of the deposition source, which can be advantageous for processing under vacuum conditions.

It will also be appreciated that the common deposition source may include other materials that are not deposited during the deposition process. For example, the common deposition source may further include copper, and the copper does not evaporate at the deposition temperatures of common fullerene and magnesium.

As an example, magnesium and C ₆₀ can be co-deposited by heating the magnesium source material and C ₆₀ source material in a Knudsen cell at a pressure of approximately 10 ⁻⁷ Torr to approximately 380 to 430° C. However, it will be appreciated by those skilled in the art that other deposition parameters may be used.

Although this method has been described with respect to evaporation for the purpose of deposition of fullerene and magnesium, it will be appreciated that various other methods can be used to deposit these materials. For example, fullerene and/or magnesium can be deposited using other physical vapor deposition (PVD) processes, such as sputtering, chemical vapor deposition (CVD) processes, or other processes known for the deposition of fullerene or magnesium. In one embodiment, magnesium is deposited by heating the magnesium source material using a resistive heater. In other embodiments, the magnesium source material may be loaded into a heated crucible, heated boat, Knudsen cell, or any other type of evaporation source. Similarly, the fullerene source material or a mixture of fullerene and magnesium source material can be loaded into a heated crucible, a heated boat, a Knudsen cell, or any other type of deposition evaporation source. Various other deposition methods can be used.

The deposition source material used for the deposition of the conductive coating layer can be a mixture or a compound, wherein at least one of the components of the mixture or compound is not deposited on the substrate during the deposition. In one example, the source material may be a Cu-Mg mixture or a Cu-Mg compound. In another example, the source material for the magnesium deposition source includes magnesium and a material with a lower vapor pressure, such as Cu. In yet another example, the source material for the co-deposition source comprises a Cu-Mg compound mixed with fullerene, such as a Cu-Mg fulleride compound. It will be appreciated that other low vapor pressure materials may be provided to the source material.

In one aspect, there is provided a product having a surface coated with a conductive coating layer, and fullerene disposed at an interface between the conductive coating layer and the surface, wherein the conductive coating layer includes magnesium.

3A shows the product according to one embodiment where the surface 107 is treated with fullerene and the conductive coating layer 200 comprising magnesium 26 is deposited on the treated surface according to an embodiment of the method as described above. To illustrate. 3A, fullerene molecules 201 are disposed at the interface between the conductive coating layer 200 including magnesium 206 and the surface 107 of the substrate 100. In the embodiment of FIG. 3A, fullerene molecules 201 are illustrated as only partially covering the interface. As described above, in the illustrated embodiment, the conductive coating layer 200 or the deposited magnesium 206 in the conductive coating layer may be in contact with the surface 107 of the substrate 100.

3B illustrates a product according to another embodiment, wherein the surface 107 is processed by depositing at least approximately a single layer of fullerene to form a fullerene layer 211, the fullerene layer of the substrate 100 The surface 107 is substantially covered. 3B, the fullerene layer 211 disposed at the interface between the conductive coating layer 200 including magnesium 206 and the surface of the substrate 100 substantially covers the interface.

3C illustrates a product according to yet another embodiment, wherein the conductive coating layer 200 includes fullerene molecules 201 dispersed throughout or within the deposited magnesium 206. The product illustrated in FIG. 3C may be produced using one of the methods described above with respect to FIG. 1 or with respect to FIG. 2.

Although the fullerene molecules 201 may not exist as dominant at the interface between the conductive coating layer 200 and the surface 107 of the substrate 100 compared to the film illustrated in FIG. 3B, the conductive coating layer 200 Can nevertheless adhere well to the surface 107 of the substrate 100. In particular, it has been found that the dispersion of the fullerene molecules 201 through the entire magnesium 206 increases the stability in the air of the magnesium film by reducing the oxidation rate of the magnesium. Based on experimental observations and prior findings, the inventors have discovered that fullerene molecules 201 dispersed throughout the magnesium 206 electronically and/or chemically interact with the magnesium 206 to increase the stability of the magnesium. Is assumed. More specifically, fullerenes are generally strong electron acceptors, and as described above, it is known that they can improve the oxidation stability of nearby magnesium atoms.

Moreover, it will be appreciated that the concentration of fullerene in the conductive coating layer can be varied throughout the coating layer. For example, the concentration of fullerene near the treated surface may be relatively low (e.g., about 2% by weight), but the concentration of fullerene in the remainder of the conductive coating layer may be relatively high (e.g., about 10% by weight). ). On the other hand, the concentration of fullerene near the treated surface is relatively high (for example, about 10% by weight) and the concentration of fullerene in the rest of the conductive coating layer may be relatively low (for example, about 2% by weight). It will be appreciated that the relative concentrations of fullerene and magnesium can be varied by adjusting various deposition parameters.

In one embodiment, the product further comprises a getterer comprising magnesium. As understood by those skilled in the art, getters are materials that are generally provided on the product or device for the purpose of improving the “storage-life” of the product or device. Getters generally eliminate adverse species, passivate, blockade, or otherwise inhibit negatively affecting the performance of the paper device. According to one embodiment, the getter is formed integrally with the conductive coating layer by depositing a relatively thick conductive coating layer comprising magnesium on the product. The getter or conductive coating layer may react with oxygen and/or water vapor present in the device packaging environment, or otherwise passivate to produce oxidation and/or magnesium hydroxide, thereby removing these molecules from the device packaging environment. have. The portion of the conductive coating layer that acts as the getter can be reduced or have a fullerene concentration of 0 to become more reactive. In another embodiment, the getter may be deposited separately from the conductive coating layer. For example, a getter containing magnesium may be deposited on the conductive coating layer.

It will be appreciated that the substrate may include organic and/or inorganic materials. Thus, it will be appreciated that the surface of such a substrate can be any organic and/or inorganic surface on which fullerenes can be deposited. For greater clarity, fullerenes can be deposited on the surface using any method or process known in the art, where the fullerenes deposited on the surface are intermolecular forces, intramolecular forces, and any other type of It will be understood that it can be weakly or strongly bonded to the surface by force, interaction and/or bonding. For example, fullerenes can be bonded to the surface by van der Waals force, electrostatic force, gravity, magnetic force, dipole-dipole interaction, non-covalent interaction, and/or covalent bonding.

It will be appreciated that as used in the present invention, an organic substrate or organic surface mainly refers to a substrate or surface comprising an organic material. For greater clarity, it will be understood that an organic material is generally any material that contains carbon, where one or more carbon atoms are covalent to another type of atom (eg hydrogen, oxygen, nitrogen, etc.). To combine. Specifically, it has been observed that a conductive coating layer containing magnesium can be deposited on the surface of an organic semiconductor material commonly used as an electroluminescent layer or electron injection layer of an organic light emitting diode using the method according to the invention. Examples of such materials include 8-hydroxyquinolinoleitolithium (Liq) and tris(8-hydroxy-quinolinato)aluminum (Alq ₃ ). Other exemplary surfaces for which the method according to the invention can be used are other organic semiconductor materials, for example 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP), 1,3, 5-tris-(N-phenylbenzimidazol-2-yl)-benzene (TPBi), bis(2-methyldibenzo[f,h]quinoxaline) (acetylacetonate) iridium(III), bis(2 -Phenylpyridine)(acetylacetonate) iridium(III), 1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene, 4,7-diphenyl-1,10-phenanthrol Lean (Bphen), 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ), Mes ₂ B[p-4,4'-bi Phenyl-NPh(1-naphthyl)] (BNPB), and N,N'-di(naphthalen-1-yl)-N,N'-diphenyl-benzidine (NPB), or various other conjugated organic materials do.

Furthermore, it will be appreciated that the method according to the invention can be used on the surface of various other materials commonly used as electron injection layers, electron transport layers and/or electroluminescent layers of organic optoelectronic devices. For example, a thin layer of an inorganic material, such as LiF, can be inserted between the organic layer and the fullerene layer, as further disclosed in the present invention. The fullerene layer can impart one or more effects to the magnesium layer, including a higher adhesion coefficient and better stability, and this effect can be beneficial. Examples of such materials include organic molecules as well as organic polymers, such as those disclosed in PCT Publication No. 2012/016074. Those skilled in the art will also appreciate that organic materials doped with various elements and/or inorganic compounds can still be considered organic materials. Additionally, those skilled in the art of fabricating organic electronic devices will appreciate that a variety of organic materials can be used and the full range of such organic materials is too much to mention in this application. However, it will also be apparent to those skilled in the art that the methods disclosed herein can be applied to such materials.

It will also be understood that an inorganic substrate or surface, as used in the present invention, is primarily understood to mean a substrate comprising an inorganic material. For greater clarity, it will be understood that the inorganic material is any material that is not generally considered to be an organic material. Examples of inorganic materials include metal, glass, and minerals. Specifically, it has been observed that a conductive coating comprising magnesium can be deposited on the surface of LiF, glass and silicon (Si) using the method according to the invention. Other surfaces to which the method according to the invention can be applied include surfaces of silicon or silicon-based polymers, inorganic semiconductor materials, electron injection materials, salts, metals, and metal oxides.

It will be appreciated that the substrate may include a semiconductor material, and thus the surface of the substrate may be a semiconductor surface. Semiconductors may be disclosed as materials that exhibit a degree of electrical conductivity that is less than a conductor (eg metal) but greater than an insulator (eg glass). It will be appreciated that the semiconductor material can be an organic semiconductor or an inorganic semiconductor. Some examples of organic semiconductor materials are listed above. Some examples of inorganic semiconductor materials include, but are not limited to, group IV element semiconductors, group IV compound semiconductors, group VI element semiconductors, group III-V semiconductors, II-VI semiconductors, I-VII semiconductors, IV-VI semiconductors, and IV-VI semiconductors. , V-VI semiconductor, II-V semiconductor, oxide and other semiconductor materials.

Moreover, it will be appreciated that the substrate may include multiple layers of organic and/or inorganic materials. For example, in the case of an organic light emitting diode (OLED), the substrate may include an electron injection layer, an electron transport layer, an electroluminescent layer, a hole transport layer, a hole injection layer and/or an anode.

For some applications, it may be desirable to selectively deposit magnesium on the portion(s) of the organic surface. For example, it may be desirable to selectively deposit magnesium on a portion of the surface to form a regular or irregular pattern on the organic surface. In one embodiment, the portion(s) of the organic surface where magnesium deposition is desired is treated by depositing fullerenes. Magnesium will selectively deposit on areas of the fullerene-treated surface, as it exhibits very low adhesion to organic molecules commonly used in organic optoelectronic devices. As above, once the desired portion(s) of the surface has been treated, the entire surface can be exposed to a magnesium source to allow the magnesium to selectively deposit on the fullerene-treated area of the organic surface. The organic surface can be selectively treated with fullerene using, for example, shadow mask deposition, contact printing, micro-contact printing, lithography, or other patterning techniques known in the art.

4 shows a shadow mask process for depositing fullerene on the surface 107 of the substrate 100 according to one embodiment. The shadow mask 302 is illustrated as having a hole or gap 308 formed in the mask, shaped corresponding to the desired pattern or shape transferred onto the surface. More specifically, when the shadow mask process is used with the evaporation process as shown in FIG. 4, holes or gaps 308 are formed in the shadow mask 302 to enter the surface of the mask 302. It will be appreciated that while suppressing the passage of evaporated source material, at the same time passing some of the evaporated source material over the shadow mask 302 and depositing it on the surface 107 of the substrate 100. Consequently, the pattern or shape of the deposited material corresponds to the pattern or shape of the hole or gap 308 formed on the shadow mask 302.

As illustrated in FIG. 4, a fullerene source 104 is provided on the surface of the shadow mask 302 opposite the substrate 100. When the fullerene source 104 orients the fullerene in the substrate 100, the shadow mask 302 inhibits the deposition of fullerene from reaching the area of the surface 107 covered by the shadow mask 302. Fullerenes on the area of the surface 107 corresponding to the holes or gaps 308 of the shadow mask 302 while creating an untreated area 303 on the surface 107 of the substrate 100 It can be deposited to create a processed region 304 on the surface 107 of the substrate 100. Although the shadow mask 302 is illustrated as having only one hole or gap 308 in the illustrated embodiment, it will be appreciated that the shadow mask 302 can include additional holes or gaps.

5A-5C illustrate a microcontact transfer printing process for depositing fullerenes on the surface of a substrate in one embodiment. Similar to the shadow mask process, a portion of the surface can be selectively treated by fullerene deposition using the microcontact printing process.

5A illustrates the first step of the microcontact transfer printing process, where a stamp 402 with a protrusion 403 is provided with a fullerene 404 on the surface of the protrusion 403. As understood by those skilled in the art, fullerene 404 can be deposited on the surface of the protrusion 403 using known methods or processes.

As illustrated in FIG. 5B, the substrate 100 is then brought into contact with the stamp 402 such that the fullerene 404 deposited on the surface of the protrusion 403 contacts the surface 107 of the substrate 100. Take it adjacent to. When the fullerene 404 contacts the surface 107, some or all of the fullerene 404 is attached to the surface 107 of the substrate 100.

As above, when the stamp 402 moves away from the substrate 100 as illustrated in FIG. 5C, some or all of the fullerene 404 is effectively on the surface 107 of the substrate 100. Is transferred.

Once fullerene has been deposited on the surface 107 of the substrate 100, magnesium can be deposited on the fullerene-treated area of the surface 107. Returning to FIG. 6, the magnesium source 102 is illustrated as evaporated magnesium directed to the surface 107 of the substrate 100. Particularly when the surface 107 is an organic surface, magnesium is deposited on the fullerene-treated area of the surface as described above, but not on the untreated area 303 of the surface. As above, the magnesium source 102 selectively directs evaporated magnesium to both the treated and untreated areas of the surface 107 to selectively select magnesium on the fullerene-treated areas of the surface 107. It can be calm. In FIG. 6, the fullerene-treated area of the surface 107 is illustrated by the fullerene 304 deposited on the surface 107. Although the shadow mask patterning and microcontact transfer printing process has been illustrated and described above, it will be appreciated that other methods and processes can be used to selectively pattern the substrate 100 by fullerene deposition. For example, the substrate can be patterned with fullerene using photolithography or reel-to-reel printing.

In one aspect, there is provided a method of reducing the deposition of magnesium on a shadow mask, the method comprising coating at least a portion of the surface of the shadow mask with an organic coating.

Although the shadow mask deposition process has been described above with reference to fullerene deposition, it will be appreciated that the process can similarly be applied to deposition of other materials such as magnesium. For example, the magnesium can be selectively deposited on the surface by directing the evaporated magnesium through a hole or gap formed on the shadow mask. The deposition process can also be repeated using the same shadow mask to selectively deposit magnesium on the outer surface. However, one disadvantage of repeatedly using the same shadow mask for deposition is that the material to be deposited can be deposited on the periphery of the hole or gap of the shadow mask, thus deforming the shape or pattern of the hole or gap. will be. This is problematic for many applications because the formation pattern or shape of the material deposited on the substrate using the same shadow mask will change with the formation of the deposition material. The formation of the deposit material around the perimeter of the hole or gap may also be difficult to remove and/or not economical. As described above, in many cases, once the formation of the deposition material causes the quality of the shadow mask to be reduced below a predetermined limit, the shadow mask is discarded. This practice increases both the waste and costs associated with such deposition processes.

However, it has now been found that by applying an organic coating layer that exhibits poor adhesion to magnesium on a shadow mask, it is possible to reduce or potentially even eliminate the formation of magnesium around the holes or crevices of the shadow mask. lost. Moreover, if it is necessary to finally clean the mask, the organic coating layer may be evaporated or dissolved to remove the organic coating layer and any material deposited on the surface from the surface of the shadow mask. In some cases, a new organic coating may then be applied to the shadow mask for later use.

Turning now to FIG. 7, a shadow mask 302 is provided that includes an organic coating layer 602 covering at least a portion of the surface of the shadow mask 302 and a hole or gap 308. In the illustrated embodiment, the organic coating layer 602 covers the surface of the shadow mask 302 facing the magnesium source 102 to reduce the likelihood of magnesium depositing on the surface of the shadow mask 602. Is provided for. As described above, the shadow mask passes evaporated magnesium through the hole 308 to deposit on the substrate surface 100, but evaporated magnesium entering the coated surface of the shadow mask 302 The passage of the restraints. More specifically, as illustrated in FIG. 7, magnesium incident on the organic coating layer 602 is not attached or deposited on the surface of the organic coating layer 602 and thus around the periphery of the hole or gap 308. No or little magnesium is formed so that the intended pattern or shape of the hole or gap 308 is not distorted.

For comparison, FIG. 8 illustrates a cross-section of an uncoated shadow mask used for deposition of magnesium. Since the shadow mask is typically made of an inorganic material such as metal, the magnesium forming portion 702 can be formed over repeated deposition. As can be seen from the figure, repeated use of the shadow mask 302 reduced the width of the hole to α'by the formation of a magnesium forming portion 702 on the periphery of the hole or gap 308. In comparison, FIG. 9 illustrates a shadow mask 302 with an organic coating layer 602 with reduced or removed magnesium formation on the surface. As illustrated in FIG. 9, magnesium incident on the organic coating layer does not adhere to the organic surface. As described above, magnesium is not formed in the periphery 311 of the hole 308, and as a result, the width α of the hole is maintained.

Although not illustrated in the drawings, it will be appreciated that other portions of the shadow mask 302 may be further coated. For example, the peripheral portion 311 of the hole or gap 308 may be coated with an organic coating layer.

It will be appreciated that the organic coating layer can include any organic material. For example, the organic coating layer may include an organic material commonly used as an active layer of an organic photovoltaic device. Examples of organic materials that can be used as the organic coating layer include polytetrafluoroethylene (PTFE) and silicon or silicon-based polymers.

It will also be appreciated that magnesium can be deposited on a fullerene-treated surface as described above or any other surface capable of depositing magnesium using an optional magnesium deposition process using a shadow mask as described above. .

Although the above method of reducing the deposition of magnesium on the surface is described with reference to a shadow mask, other deposition devices and/or components may be treated with an organic coating layer to reduce the deposition of magnesium on the surface of such devices and/or components. You will know that you can. For example, the walls of the viewing window or baffle system of the chamber can be similarly coated with an organic coating to reduce unwanted formation of magnesium on a particular surface.

In another aspect, an organic electronic device is provided, the organic electronic device comprising an anode and a cathode (the cathode includes magnesium), an organic semiconductor layer interposed between the anode and the cathode, and the organic semiconductor layer. Includes fullerenes placed between cathodes.

In yet another aspect, an organic optoelectronic device is provided, the organic optoelectronic device comprising an anode and a cathode (the cathode comprises magnesium), an organic semiconductor layer interposed between the anode and the cathode, and the organic semiconductor layer And a fullerene disposed between the cathode.

As is known, optoelectronic devices are generally any device that converts electrical signals into photons or vice versa. As described above, an organic optoelectronic device, as used in the present invention, will be understood to be any optoelectronic device in which the active layer(s) of the device is formed primarily of an organic material, and more specifically of an organic semiconductor material. Examples of organic optoelectronic devices include, but are not limited to, organic light emitting diodes (OLEDs) and organic photovoltaic cells (OPVs).

In one embodiment, the organic optoelectronic device is an organic light emitting diode, wherein the organic semiconductor layer comprises an electroluminescent layer. In other embodiments, the organic semiconductor layer may include additional layers, such as an electron injection layer, an electron transport layer, a hole transport layer, and/or a hole injection layer.

In one embodiment, fullerene is disposed at the interface formed between the organic semiconductor layer and the cathode. In some cases, where the organic semiconductor layer includes an additional layer, fullerene may be disposed at an interface between the layer closest to the cathode and the cathode. For example, fullerene may be disposed at the interface created between the electron injection layer and the cathode.

In one embodiment, the organic optoelectronic device further comprises a getter, and the getter comprises magnesium. In another embodiment, the getter is formed integrally with the conductive layer. The getter can be formed integrally with the conductive layer, for example, by depositing a relatively thick conductive layer so that a portion of the conductive coating layer acts as the getter. For example, the conductive coating layer may be hundreds of nanometers, hundreds of microns, or more to enable long-term gettering of water vapor and oxygen that may be present in the packaged product.

Providing a getter for a phosphorescent OLED device can be particularly advantageous because the phosphorescent OLED device contains a phosphorescent light emitting layer that may be extinguished in the presence of oxygen. By providing a getter, it is possible to significantly reduce the concentration of oxygen in the packaged environment of the phosphorescent OLED device, thus reducing the rate of deterioration of the phosphorescent layer.

It will be appreciated that as used herein, fullerenes are understood to be any carbon-based molecule in the form of a hollow sphere, ellipsoid, tube, or any other three-dimensional shape. More specifically, it will be understood that fullerenes include carbon-based molecules in which atoms are arranged in closed hollow spheres, as well as carbon-based molecules in which atoms form an elongated hollow tube structure. As above, examples of fullerenes include, but are not limited to, buckminster fullerene (i.e., C ₆₀ ), C ₇₀ , C ₇₆ , C ₈₄ , multi-walled and single-walled carbon nanotubes (CNT) (including conductive and semi-conductive carbon nanotubes). It includes. It will be appreciated that fullerenes can also be a combination or mixture of many different types of fullerenes. Moreover, it will be appreciated that fullerene derivatives, such as functionalized fullerenes, as well as doped fullerenes, can be used for the purposes of the present invention. As above, the fullerene molecule may contain various functional groups and/or non-carbon atoms. For example, phenyl-C61-butyric acid methyl ester (PCBM) can be used as the fullerene.

It will also be appreciated that the magnesium disclosed herein can be substantially pure magnesium or a magnesium alloy. It will be appreciated that the purity of substantially pure magnesium may be 95% or more, 98%, 99%, 99.9%, or more. Magnesium alloys can include various magnesium alloys known in the art.

Example

The aspects of the present invention will now be illustrated with reference to the following examples, which are not intended to limit the scope of the invention in any way.

The molecular structure of the different organic materials used in the exemplary embodiments is provided below.

As understood, CBP is 4,4'-bis(N-carbazolyl)-1,1'-biphenyl, Alq ₃ is tris(8-hydroxy-quinolinato)aluminum, and TPBi is 1 ,3,5-tris-(N-phenylbenzimidazol-2-yl)-benzene, Ir(MDQ) ₂ (acac) is bis(2-methyldibenzo[f,h]quinoxaline) (acetylaceto Nate) Iridium(III), Ir(ppy) ₂ (acac) is Bis(2-phenylpyridine)(acetylacetonate)Iridium(III), TmPyPB is 1,3,5-tri[(3-pyridyl )-Phen-3-yl]benzene, Bphen is 4,7-diphenyl-1,10-phenanthroline, and TAZ is 3-(4-biphenyl)-4-phenyl-5-tert-butyl Phenyl-1,2,4-triazole, BNPB is Mes ₂ B[p-4,4'-biphenyl-NPh(1-naphthyl)], NPB is N,N'-di(naphthalene-1 -Yl)-N,N'-diphenyl-benzidine, Liq is 8-hydroxyquinolinolato-lithium, HATCN is hexacarbonitrile, a-NPD is 4,4-bis[N-(1 -Naphthyl)-N-phenyl-amino]biphenyl.

Turning now to FIG. 10, an exemplary red phosphorescent OLED 1000 comprising a magnesium cathode is provided. The OLED device 1000 was manufactured according to the following procedure. A standard regime of Alconox (trademark) dissolved in deionized water (DI), acetone and methanol in a transparent conductive anode 1014 of indium-doped tin oxide (ITO) coated on a glass substrate 1016. (regiment) was washed by ultrasonic waves. Subsequently, UV ozone treatment was applied to the ITO substrate 1014 for 15 minutes in a photo surface processing chamber (Sen Lights). A 1 nm-thick high work function MoO ₃ layer 1012 was then deposited on the ITO anode 1014.

A 50 nm-thick CBP hole transport layer (HTL) 1010 was then deposited on the MoO ₃ layer 1012. A 15 nm-thick red light emitting layer 1008 of a CBP host doped with a phosphorescent red emitter Ir(MDQ) ₂ (acac) was deposited on the CBP layer 1010. The CBP host was doped to a concentration of 4% by weight.

A 65 nm-thick TPBi electron transport layer (ETL) 1006 was deposited on the red phosphorescence emitting layer 1008. A 1 nm-thick LiF layer 1004 was deposited on the TPBi layer 1006. A 100 nm-thick Al or Mg cathode layer 1002 was deposited on the LiF layer. In the case of the magnesium cathode, a full angstrom-thick fullerene adhesion promoting layer comprising C ₅₀ was deposited on top of the LiF layer prior to the deposition of magnesium. When various attempts were made without the use of the fullerene adhesion promoting layer in the fabrication of the device, the magnesium was deposited as a non-conductive oxide layer that would not adhere to the substrate or render the device inoperable during the deposition process. The OLED 1000 was driven by a power supply 1020.

It has also been found that although the LiF layer 1004 was deposited prior to the deposition of fullerene in this example, the LiF layer could also be deposited between the deposition of fullerene and magnesium and still a successful deposition of magnesium could be produced. The inventors may be the result of this relatively small LiF molecule moving through the deposited fullerene to occupy the gap site in the fullerene adhesion promoting layer, thus exposing some fullerene molecules on the surface, which is for subsequent magnesium deposition. It is assumed to act as a nucleation site.

It will be appreciated that various other materials can be used for the electron injection layer (EIL). For example, 8-hydroxyquinolinoleitolithium (Liq) and LiF are common EIL materials. Other examples of materials suitable for use as the EIL include, but are not limited to, metal fluorides (eg LiF, NaF, KF, RbF, CsF, BaF ₂ ), cesium carbonate (Cs ₂ CO ₃ ), lithium cobalt oxide (LiCoO ₂ ), LiO ₂ , pure metals (eg Ca and Cs) and organic metals doped with n-type dopants. However, those skilled in the art will appreciate that various other EIL materials may be used. It will also be appreciated that depending on the special structure of the OLED device, the EIL layer may not be present.

It will also be appreciated that the LiF layer can be deposited before or after the deposition of the fullerene adhesion promoting layer, and the order of deposition of other EIL materials may have a greater impact on the subsequent deposition of magnesium and the operation of the resulting OLED device. . In particular, as mentioned above, it is assumed that the small size of the LiF molecule allows LiF to move through the gap of the fullerene adhesion promoting layer. However, the ability of other materials suitable for use as the EIL to move through the gap of the fullerene adhesion promoting layer is the size of the molecule, the density and size of the fullerene in the adhesion promoting layer, and the fullerene and EIL materials. It will vary according to other specific properties.

The device manufactured according to the above process was characterized for measuring the comparative performance of an OLED device comprising a magnesium cathode for the same OLED device comprising an aluminum cathode for the device structure of FIG. 10. As further disclosed in the present invention, various other OLED devices were fabricated to further analyze the effect of providing fullerene to an OLED device having a magnesium cathode.

11 shows a plot of current density as a function of voltage for the red phosphorescent OLED device 1000 of FIG. 10 with an aluminum or magnesium cathode. As can be seen from the above plot, the current density of an OLED device comprising a magnesium cathode is hardly distinguishable from the current density of an OLED device comprising an aluminum cathode over a wide voltage range. These similar results demonstrate that the charge injection properties of the magnesium electrode are similar to those of the aluminum electrode in the OLED device 1000.

Standardized electroluminescence intensity as a function of wavelength for a red phosphorescent OLED device comprising aluminum and magnesium cathodes was measured using an OceanOptics USB4000 Fiber Optic spectrometer with an integrating sphere. Each of the OLED devices was loaded on the entrance hole of the integrating sphere during the measurement.

As can be seen from the plot of Figure 12, the electroluminescence intensity normalized as a function of wavelength is almost the same for both devices. Specifically, an OLED device comprising a magnesium cathode exhibits an electroluminescence intensity that is almost the same as that of an equivalent device having an aluminum cathode, over the entire visible spectrum. In particular, emission peaks at 600 nm are observed for both devices, indicating that the color of light produced by the device does not shift much by the choice of cathode material selected between magnesium and aluminum.

An important measure of OLED device efficiency is external quantum efficiency (EQE). FIG. 13 shows a plot of the EQE versus the brightness of OLED devices having the structure illustrated in FIG. 10. The first device included a magnesium cathode and the second device an aluminum cathode. Similar to the electroluminescence intensity results, the EQE was measured using an Oceanoptics USB4000 fiber optic spectrometer with an integrating sphere. As can be seen from the plot of FIG. 13, both devices are less efficient with increasing luminance, but the device with the magnesium cathode generally exhibits a higher EQE than the device with the aluminum cathode. .

For example, at a luminance of 1000 cd/A, the device comprising the magnesium cathode exhibited an EQE of approximately 11.25%, while an equivalent device with the aluminum cathode exhibited an EQE of approximately 9.75%. This suggests that the use of a magnesium cathode rather than an aluminum cathode increases the EQE of the OLED device in this embodiment.

The improved EQE can be explained by the higher reflectance of magnesium compared to that of aluminum at the emission peak of 600 nm (which corresponds to the peak wavelength emitted by both devices), as shown in FIG. 12. Higher reflectivity causes a larger proportion of photons entering the cathode to be reflected, thus increasing the likelihood that the reflected photons exit the device through the optically transparent anode 1014. Since the EQE is a percentage of the number of photons emitted by the device relative to the total number of charges injected into the device, it can be seen that having a more reflective cathode can result in an increase in the EQE of the device.

The reflectance of the magnesium and aluminum was measured, and as shown in FIG. 14, the reflectance of magnesium was found to be greater than the reflectance of aluminum over the entire visible spectrum (including at 600 nm). To obtain the plot of FIG. 14, aluminum and magnesium films with a thickness of about 100 nm were deposited on a glass substrate and the reflectance of the films was PerkinElmer LAMBDA 1050 UV/Vis/ with a 150 mm integrating sphere accessory. It was measured using a NIR spectrophotometer. It is noted that a 10 mm thick fullerene adhesion promoting layer was deposited on the glass substrate before the deposition of magnesium. The reflectance of the films was measured from the glass side of the film, and the results were not corrected for reflection at the air/glass interface (which is estimated to be approximately 4%).

It can be seen from FIG. 14 that the reflectance of magnesium is higher than that of aluminum over the entire visible spectrum. In particular, at longer wavelengths of the visible spectrum corresponding to the red region of the spectrum, the difference in reflectance becomes more pronounced. The results presented in FIG. 14 suggest that a device with a magnesium cathode can exhibit relatively good light extraction compared to a device with an aluminum cathode, especially for red OLED devices.

It was also observed that the extinction coefficient k of C ₆₀ was highest near the blue region of the visible spectrum. As recognized, the extinction coefficient refers to the imaginary component of the refractive index of the material. A plot of k versus wavelength for a C ₆₀ sample is shown in FIG. 15. The extinction coefficient was measured using spectroscopic ellipsometry.

15, it can be seen that C ₆₀ absorbs more in the blue region (ie, about 400 to 500 nm) of the visible spectrum than in the green or red region (ie, about 500 to 800 nm) of the visible spectrum. This suggests that the output of a red OLED with a magnesium cathode will be less affected by the absorbance by the C ₆₀ adhesion promoting layer compared to the output of the same blue OLED device. It is noted that the absorbance is higher in the blue region of the visible spectrum in the case of C ₆₀ , but the effect of absorbance by the fullerene adhesion promoting layer can be reduced, for example, by using a very thin adhesion promoting layer of approximately 1 Angstrom. In devices where fullerenes are dispersed throughout the magnesium-based cathode, the concentration of fullerenes in the cathodes can be kept low to reduce absorbance across the visible spectrum.

Example OLED device structure for cathode material characterization Emitter material Device structure Ir(MDQ) ₂ (acac) ITO/MoO ₃ (1 nm)/CBP (50 nm)/CBP:Ir(MDQ) ₂ (acac) (4%, 15 nm)/TPBi (65 nm)/LiF (1 nm)/cathode (100 nm) ) Alq ₃ ITO/MoO ₃ (1 nm)/NPB (45 nm)/Alq ₃ (60 nm)/LiF (1 nm)/cathode (100 nm) Ir(ppy) ₂ (acac) ITO/MoO ₃ (1 nm)/CBP (35 nm)/CBP:Ir(ppy) ₂ (acac) (8%, 15 nm)/TPBi (65 nm)/LiF (1 nm)/cathode (100 nm ) BNPB ITO/MoO ₃ (1 nm)/CBP (40 nm)/TPBi:BNPB (10%, 10 nm)/TPBi (60 nm)/LiF (1 nm)/cathode (100 nm)

Performance performance of OLED devices in Table 2 Emitter material Emission peak (nm) EQE (%) at 1,000 cd/m ² for Al cathode EQE (%) at 1,000 cd/m ² for Mg cathode Ir(MDQ) ₂ (acac) 600 9.9 11.2 Alq ₃ 526 1.3 1.3 Ir(ppy) ₂ (acac) 522 24.2 24.2 BNPB 456 3.1 3.1

Table 2 provides four device structures used to compare the performance of magnesium cathodes to aluminum cathodes. Specifically, the OLED device was manufactured according to the device structure listed in Table 2 using a magnesium cathode or an aluminum cathode. Table 2 also lists the emitter materials used in the fabrication of each of these devices. Ir(MDQ) ₂ (acac) and Ir(ppy) ₂ (acac) are commonly used red and green phosphorescent emitters, respectively. Alq ₃ and BNPB are commonly used green and blue fluorescent emitters, respectively. As in the exemplary device illustrated in FIG. 10, a layer of C ₆₀ of 1 Angstrom thickness was deposited on the LiF layer prior to the attachment of the magnesium film in the fabrication of each device.

Table 3 shows the device performance performance characteristics for each of the devices outlined in Table 2. The emission peaks for each device were determined from the electroluminescence spectra measured using an Oceanoptics USB4000 fiber optic spectrometer with integrating sphere. External quantum efficiency was also measured using an Oceanoptics USB4000 fiber optic spectrometer with integrating sphere. Luminance was measured using a Minolta LS-110 luminance meter.

It can be seen from the EQE measurement results provided in Table 3 that the device with the magnesium cathode exhibited approximately the same efficiency as the device with the aluminum cathode. A red emitter OLED device comprising an Ir(MDQ) ₂ (acac) emitter together with a magnesium cathode was observed to exhibit slightly higher EQE compared to an equivalent device with an aluminum cathode. As described above, this can be attributed to the higher reflectivity of magnesium compared to aluminum in the red region of the visible spectrum.

The results in Table 3 indicate that the magnesium cathode attached on the fullerene adhesion promoting layer can be effectively used in place of the aluminum cathode for various device structures, along with various emitter materials. The results in Table 3 also suggest that magnesium cathodes can be used in place of aluminum cathodes in OLED devices that emit multiple colors, for example white OLED devices. Any color shift in the emission spectrum due to differences in reflectivity could be overcome by optimization of the OLED device. Multi-emitter devices (eg white OLED devices) may also be adjusted following fabrication.

Comparison of performance characteristics for Mg to Al cathodes in devices using various electron transport layers Electron transport layer material About the Al cathode
EQE at 1,000 cd/m ² (%) EQE (%) at 1,000 cd/m ² for Mg cathode TPBi 24.2 24.2 Alq ₃ 22.5 21.7 Bphen 18.6 18.7 TAZ 20.4 19.6 TmPyPb 20.6 20.0

Table 4 provides a comparison of device performance characteristics for devices comprising magnesium and aluminum cathodes with various electron transport layers (ETLs). Since the ETL is very close to the cathode and various ETL materials can be used depending on the specific device configuration, it is advantageous to have a cathode material that can be used for various materials commonly used as ETL.

Specifically, various green phosphorescent OLED devices were manufactured according to the following device structure: ITO/MoO ₃ (1 nm)/CBP (35 nm)/CBP:Ir(ppy) ₂ (acac) (8%, 15 nm) /TPBi (10 nm)/ETL (55 nm)/LiF (1 nm)/cathode (100 nm), wherein the ETL material is one of the five materials listed in Table 4. A 1 Angstrom thick C ₆₀ adhesion promoter layer was deposited on top of the LiF layer prior to deposition of magnesium for each device with a magnesium cathode. The thickness of the ETL and fullerene adhesion promoting layers was not optimized for any of the above devices to allow comparable performance for aluminum and magnesium cathodes to be compared. As above, the device performance is different between each device due to different mobility, optical properties, and interfacial properties of different ETL materials. However, for the purpose of comparing the performance of magnesium cathode to aluminum cathode, the change in device performance due to the use of different ETL materials is inappropriate.

The EQEs provided in Table 4 were measured using an Ocean Optics USB4000 fiber optic spectrometer with integrating sphere. Luminance was measured using a Minolta LS-110 luminance meter. From the EQE measurements, it can be seen that the device with the magnesium cathode exhibited a similar EQE to the same device with the aluminum cathode. These results demonstrate that magnesium can be used as a cathode material instead of aluminum by using a fullerene adhesion promoting layer for devices with various ETL materials. Specifically, it has been found that the EQE of an OLED device is substantially unaffected by the choice of cathode between magnesium and aluminum for any of the ETL materials provided in Table 4.

Turning now to Figure 16, a plot of current density as a function of voltage for a green phosphorescent OLED comprising a fullerene adhesion promoting layer of various thickness (or coverage in the case of an inner monolayer) is provided. The fullerenes used in this example consist mainly of C ₆₀ , but other types of fullerenes may also be present. The configuration of the device used to obtain the results shown in Figure 16 is as follows: ITO/MoO ₃ (1 nm)/CBP (35 nm)/CBP:Ir(ppy) ₂ (acac) (8%, 15 nm)/TPBi (65 nm)/LiF (1 nm)/C ₆₀ ( x Angstrom)/Mg (100 nm), where the values of x are 1, 5, 10, 20, 30, and 50.

In the absence of the fullerene adhesion promoting layer, magnesium did not adhere to the substrate during deposition, or was deposited primarily as a non-conductive oxide layer. Therefore, the devices manufactured without using the fullerene adhesion promoting layer were not functional and, as described above, were not included in the plot of FIG. 16.

Moreover, it can be seen that the thickness of the fullerene layer has little, if any, effect on the current density at any given voltage. As described above, fullerene deposition is firm and is substantially coverage/thickness independent in the manufacture of OLEDs containing magnesium cathodes. This makes fullerene deposition and/or patterning using various techniques suitable for the production of efficient OLED devices.

Similarly, FIG. 17 shows the EQE versus thickness of the fullerene layer for the devices. The external quantum efficiency was measured at a luminance of 1,000 cd/m 2 using an Ocean Optics USB4000 fiber optic spectrometer with an integrating sphere. Luminance was measured using a Minolta LS-110 luminance meter. It can be seen from FIG. 17 that the thickness of the fullerene adhesion promoting layer did not significantly affect the EQE under the thickness up to about 10 Angstroms. At thicknesses above 10 Angstroms, the EQE is assumed to gradually decrease in efficiency with increasing thickness. It is presumed that the gradual decrease in efficiency due to the increase in the fullerene layer thickness is due to the increase in absorbance by the fullerene. In addition, as shown in Fig. 15, the absorbance of C ₆₀ varies with wavelength. As above, this suggests that the rate of decrease in efficiency with increasing thickness of the fullerene layer varies with the emission wavelength of the OLED device.

18 shows the current density as a function of voltage for a green phosphorescent OLED device comprising aluminum and magnesium cathodes. In this example, the cathode of the device was patterned using various methods. The general device structure of the OLED device tested in this example is as follows: ITO/MoO ₃ (1 nm)/CBP (50 nm)/CBP:Ir(ppy) ₂ (acac) (8%, 15 nm)/ TPBi (65 nm)/LiF (1 nm)/cathode (100 nm). A one angstrom-thick layer of fullerene containing C ₆₀ was deposited on the LiF layer prior to the deposition of the magnesium to the magnesium cathode device.

The aluminum cathode was patterned using a shadow mask process as previously described. Two devices with magnesium cathodes were created and each magnesium cathode was deposited using one of the following two methods. In the first method, the fullerene adhesion promoting layer was deposited on the entire substrate and then magnesium was deposited using a shadow mask process to selectively deposit the magnesium cathode on a portion of the treated surface. The second method involved selectively treating a portion of the surface by depositing a fullerene adhesion promoting layer using a shadow mask process and then directing the evaporated magnesium over the entire substrate. As described above, the magnesium was only attached to the treated area of the substrate, thus forming a magnesium cathode.

It can be seen from FIG. 18 that all three devices exhibited similar current densities with respect to voltage. In particular, the magnesium cathode deposited on the patterned adhesion promoting layer showed similar performance for the device produced by depositing magnesium using a shadow mask process. Specifically, all three devices were found to exhibit similar short circuits of about 2.8 V or less. This suggests that magnesium can be produced without conductive leak paths between adjacent cathode lines of all devices, including cases deposited on a patterned fullerene adhesion promoting layer. Thus, an efficient OLED device can be fabricated using a fullerene-patterned substrate for magnesium deposition.

EQE of OLED devices containing Mg and Al patterned cathodes Cathode material EQE (%) at 1,000 cd/m ² Mg (shadow mask) 24.2 Al (shadow mask) 24.2 Mg (no shadow mask) 25.3

Regarding Table 5, a summary of device performance for the device of FIG. 18 is provided. From external quantum efficiency measurements, it can be seen that a device with a magnesium cathode deposited on a patterned fullerene adhesion promoting layer has similar or possibly higher efficiency than other devices. It suggests that the efficiency of the device is higher, due to contamination from the shadow mask used for the deposition of the material for the other two devices. Specifically, contaminants are desorbed from the mask during the metal deposition process, thereby contaminating the magnesium film and reducing interfacial quality. Table 5 shows that an OLED device comprising a magnesium cathode deposited on a patterned fullerene adhesion promoting layer can be used in place of the aluminum cathode produced using traditional shadow mask deposition techniques.

Another important device characteristic is power efficiency. 19 shows power efficiency as a function of brightness for a green phosphorescent OLED comprising a magnesium cathode as lumens/watt (Im/W). The device structure is ITO/MoO ₃ (1 nm)/CBP (35 nm)/CBP:Ir(ppy) ₂ (acac) (8%, 15 nm)/TPBi (65 nm)/LiF (1 nm)/magnesium (100 nm). The magnesium cathode was deposited according to one of two procedures. In one process, a 30 Angstrom-thick fullerene adhesion promoting layer containing C ₆₀ was deposited on the LiF layer prior to the deposition of magnesium. In another procedure, fullerenes containing C ₆₀ were co-deposited with magnesium. The fullerenes and magnesium were deposited from sublimation sources separated at various concentrations on a weight basis. For the co-deposited cathode, the composition was measured by weight using a crystal oscillator scale.

As can be seen from FIG. 19, devices having a magnesium cathode deposited over a 30 Angstrom-thick fullerene adhesion promoting layer exhibited similar power efficiency at any given luminance for the device where the cathode was co-deposited. This demonstrates that the fullerene adhesion promoting layer can be formed by co-depositing fullerene and magnesium at a concentration as low as 1 wt% to at least 10 wt%, thereby reducing the number of processing steps in the device manufacturing process. Moreover, since the OLED performance is not so dependent on the concentration of fullerene in the magnesium cathode, the processing conditions require precise control of deposition parameters to achieve the desired cathode properties for many applications. I never do that.

Referring now to Fig. 20, a plot showing the normalized brightness of a green phosphorescent OLED device over time is provided to illustrate the decrease in brightness as the device lifetime. The luminance was normalized to its initial value and the device was operated at a current density of 20 mA/cm 2. The typical device structure was ITO/MoO ₃ (1 nm)/NBP (45 nm)/Alq ₃ (60 nm)/LiF (1 nm)/cathode (100 nm). The cathode of each device was one of the following: an aluminum cathode, a magnesium cathode deposited on a 1 Angstrom fullerene adhesion promoting layer, and a 10% by weight fullerene and co-deposited magnesium cathode. Fullerenes used in the above exemplary devices included C ₆₀ . The device was encapsulated in a glass cap using UV curable epoxy in a nitrogen filled glove box prior to testing.

It can be seen from FIG. 20 that the luminance of the device with the magnesium cathode was observed to collapse at a slower rate than the same device with the aluminum cathode. This suggests that a device with a magnesium cathode is more stable than a corresponding device comprising an aluminum cathode. Moreover, the results indicate that devices comprising magnesium cathodes will generally retain their electroluminescent properties for a longer period of time than those comprising aluminum cathodes, thereby providing an OLED device with a longer operating life. Hints.

Further, as can be seen from FIG. 20, the luminance of the OLED device comprising the co-deposited magnesium and fullerene electrode 2002 is more than the device comprising the magnesium electrode deposited on the fullerene adhesion promoting layer 2004. Collapses slowly. As above, devices with magnesium-fullerene cathode 2002 may have a longer operating life than with pure magnesium cathode 2004.

Luminance decay of OLED devices containing various cathodes Cathode material Time (time) up to 90% of initial luminance Mg with 1 Å C ₆₀ 72.8 Al 63.4 Mg with 10% C ₆₀ 88.4

Table 6 shows the time (time) until the OLED device of FIG. 20 decreased to 90% of its original luminance (often referred to as T ₉₀ ). From Table 6, it can be seen that the device having the magnesium cathode deposited on the 1 Angstrom fullerene adhesion promoting layer has been found to have a longer lifespan than the device having the aluminum cathode. Moreover, it has been found that devices with co-deposited magnesium-fullerene cathodes (2002) have a longer lifetime than the other two tested devices. This suggests that devices comprising magnesium cathodes, and especially devices with magnesium-fullerene cathodes 2002, have a longer operating life than equivalent devices with aluminum cathodes.

Turning now to FIG. 21, a plot of current efficiency versus luminance of an OLED device is provided. The device was made by depositing a magnesium cathode on two different fullerene adhesion promoting layers. One adhesion promoting layer was mainly composed of C ₆₀ , while the other adhesion promoting layer was mainly composed of C ₇₀ . It will be appreciated that in addition to the main components, other components present in the fullerene layer may also be present.

As can be seen from Figure 21, the efficiency of the device was found to be similar regardless of the fullerene used. The results suggest that fullerenes other than C ₆₀ and C ₇₀ can be used to deposit magnesium instead of or in addition to C ₆₀ and/or C ₇₀ . For example, a mixture of 50% by weight of C ₆₀ and 50% by weight of C ₇₀ can be used. Other types of fullerenes that can be used include other polyhedral fullerenes, for example spherical fullerenes, tubular fullerenes, for example CNTs, fullerene rings, and the like. However, it will be appreciated that the optimum fullerene layer thickness or optimum concentration of fullerene in magnesium may differ depending on the type of fullerene used. Since the inventors assume that the fullerenes act as nucleation sites for the deposition of magnesium, larger fullerenes can provide a larger starting site. Similarly, longer fullerenes can provide an extended initiation site. As described above, the concentration and proportion of fullerene used to treat the surface to deposit magnesium on the substrate can be selected based on factors such as the shape and size of the fullerene.

UV photoelectron spectroscopy experiments were performed to further investigate the interaction between magnesium and fullerene. A plot showing ultraviolet (UV) photoelectron intensity as a function of binding energy for three thin film samples is provided in FIG. 22. One sample contained only C ₆₀ . The other two samples are C ₆₀ (Mg:C ₆₀ ) co-deposited with magnesium, and magnesium deposited on a C ₆₀ adhesion promoting layer (C ₆₀ /Mg). The samples were analyzed using an ultraviolet photoelectron spectrometer with He 1α (hv = 21.22 eV) in a PHI 5500 multi-technology system at a base pressure of about 10 ^-10 Torr.

The scale of FIG. 22 refers to the Fermi level (ie 0 eV binding energy) of the sputter washed Au substrate in electrical contact with the sample. The peak occupied molecular orbit (HOMO) peak appears as a binding energy of about 2.5 eV across the spectrum. The HOMO-1 derived peak also appears across the spectrum with a binding energy of 3.6 to 3.7 eV. A small feature in the C ₆₀ spectrum at approximately 0.5 eV is the artifact from the He 1β (hv = 23.09 eV) satellite line that excites the HO ₆₀ of C ₆₀ .

From FIG. 22, it can be seen that as the HOMO-1 peak moves to a lower binding energy, the half width (FWHM) of the HOMO and HOMO-1 induced peaks increases. This indicates that the chemical bonding energy between the carbon atoms in the fullerene decreases and suggests a new bonding structure. Moreover, new features appear in the spectrum between the HOMO derived peak and the Fermi level for magnesium deposited on the C ₆₀ and C ₆₀ thin films co-deposited with the magnesium. The movement of the Fermi level also indicates that a new bond structure has been formed, and the decrease in bandgap indicates that the change in the bond structure is associated with an increase in conductivity.

These characteristic features are consistent with the photoelectron spectrum of magnesium fulleride, as provided in Physical Review B 45, 8845 (1992). As above, the above suggests that charge transport occurs between the magnesium and fullerene. These features also suggest that magnesium fulleride is formed for both the C ₆₀ and C ₆₀ thin films co-deposited with the magnesium. As described above, in the case of a device having a magnesium cathode deposited on a fullerene adhesion promoting layer, magnesium fluride may be formed at the interface between the magnesium cathode and the ETL.

Performance of devices with various cathode structures Cathode structure Driving voltage (V) at 20 mA/cm ² Luminance at 500 mA/cm ² (cd/m ² ) Power efficiency at 20 mA/cm ² (Im/W) Al 8.3 3,530 0.63 LiF/Al 5.9 19,900 2.2 C ₆₀ /Al 8.3 - - C ₆₀ /LiF/Al 5.8 19,700 2.3 LiF/C ₆₀ /Al 5.8 19,800 2.3 Mg 11 30 0.02 LiF/Mg - - - C ₆₀ /Mg 8.1 9,810 0.86 C ₆₀ /LiF/Mg 6.0 21,200 2.4 LiF/C ₆₀ /Mg 6.0 21,100 2.4

Table 7 provides a summary of device performance for green fluorescent devices with various cathode structures. The basic device structure of the devices tested was as follows: ITO/CuPC(25 nm)/NBP(45 nm)/Alq ₃ (60 nm)/cathode structure. For each of the various cathode structures, the thickness of the LiF layer was approximately 1 nm, the thickness of the fullerene layer containing C ₆₀ was approximately 3 nm, and the thickness of the Al and Mg layers was approximately 100 nm. Luminance was measured using a Minolta LS-110 luminance meter.

From Table 7, the use of a fullerene adhesion promoting layer comprising C ₆₀ between the Li layer and the Al cathode, or between the Alq ₃ layer and the LiF layer, does not significantly drive, voltage, brightness or power efficiency of the device comprising the aluminum cathode. It can be seen that it does not change. It is also noted that the device with the C ₆₀ /Al cathode structure did not emit any detectable light below the current density of about 500 mA/cm 2. It is noted that the LiF/Mg cathode or the pure magnesium cathode without the fullerene adhesion promoting layer did not work or showed poor performance because the entire magnesium cathode of the device was oxidized.

From Table 7, it can also be seen that the device performance of C ₆₀ /LiF/Mg is similar to that of LiF/C ₆₀ /Mg cathode structure. Moreover, these cathode structures are similar in performance to comparable devices with aluminum cathodes. This implies that in the case of a sufficiently thin electron injection layer containing a small molecule (for example, 1 nm thick LiF), the fullerene adhesion promoting layer can be attached before or after the electron injection layer.

The effect of EIL material selection and deposition sequence on the device performance was further studied by measuring the performance of two exemplary green fluorescent OLED devices. In particular, both devices were manufactured using 8-hydroxyquinolinoleitolithium (Liq) as EIL. For the first device, the cathode structure was fabricated by depositing fullerene on the EIL and then magnesium cathode on the fullerene treated surface. However, in the case of the second device, the cathode structure, the fullerene is deposited on the organic layer, and then the EIL and magnesium cathodes are deposited on top of the EIL so that the fullerenes and magnesium cathodes are separated by the Liq EIL. It was produced by effectively creating a sword structure.

Specifically, each of the OLED devices was manufactured according to the following procedure. The transparent conductive anode of ITO was coated on a glass substrate and washed by ultrasonic waves with a standard regime of deionized water (DI), acetone, and Alconox (trademark) dissolved in methanol. The ITO substrate was then subjected to UV ozone treatment for 15 minutes in a photo surface processing chamber (Sen Rights). Then a 1 nm-thick high work function MoO ₃ layer was deposited on the ITO anode. Then a 25 nm-thick 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HATCN) hole transport layer (HTL) was deposited on the ITO layer as a hole injection layer. A 45 nm-thick a-NPD hole transport layer was then deposited on the HATCN layer. Each device was created by depositing a 60 nm-thick Alq3 green light emitting layer on the HTL and then the cathode structure described above on the light emitting layer.

The first structure included a 1 nm Liq layer deposited on the emissive layer, followed by a 3 nm C ₆₀ fullerene layer, and finally a 500 nm thick magnesium cathode. On the other hand, the second cathode structure included a 3 nm C ₆₀ fullerene layer deposited on the light emitting layer, followed by a 1 nm Liq EIL and a 500 nm thick magnesium cathode. The measurements taken from both devices are summarized in Table 8 below.

Effect of cathode structure on device efficiency Cathode structure Driving voltage (V) at 20 mA/cm ² Luminance at 500 mA/cm ² (cd/m ² ) Power efficiency at 20 mA/cm ² (Im/W) Liq/C ₆₀ /Mg 4.9 18990 2.41 C ₆₀ /Liq/Mg 7.1 - 0.63

As shown in Table 8, unlike the cases where LiF is used as EIL, the order of material deposition when Liq is used as EIL has a significant effect on the performance of the device. The inventors assume that because the Liq molecule is significantly larger than the LiF molecule, it seems to be due to Liq failing to penetrate the fullerene layer as effectively as LiF.

Regarding Table 8, it can be seen that the deposition order of the EIL with respect to the fullerene had a significant effect on the performance of the device. For example, a device with a fullerene layer disposed adjacent to a magnesium cathode exhibited a drive voltage of about 4.9 V at 20 mA/cm 2, while the same device with a Liq layer disposed between fullerene and magnesium cathode was 20 7.1 V was required to run at mA/cm 2. Similarly, the luminance of the first device was measured to be 18990 cd/m 2 at 500 mA/cm 2, while the second device did not emit any detectable light when running at 500 mA/cm 2. Moreover, it is noted that the power efficiency of the first device is substantially greater than the power efficiency of the second device.

To compare the shelf life of a device comprising a magnesium cathode to the same device comprising an aluminum cathode, an exemplary OLED device comprising two different cathode materials was fabricated and stored at ambient conditions. More specifically, for the purpose of studying the effects caused by exposure of the device to air, the devices are not encapsulated in any packaging in this embodiment.

Each of the two exemplary green fluorescent OLED devices was manufactured according to the following procedure. The transparent conductive anode of ITO was coated on a glass substrate and washed by ultrasonic waves with a standard regime of deionized water (DI), acetone, and Alconox (trademark) dissolved in methanol. The ITO substrate was then subjected to UV ozone treatment for 15 minutes in a photo surface processing chamber (Sen Rights). Then a 1 nm-thick high work function MoO ₃ layer was deposited on the ITO anode. Then a 45 nm-thick a-NPD hole transport layer (HTL) was deposited on the MoO ₃ layer 1012. A 60 nm-thick Alq3 green light emitting layer was deposited on the a-NPD HTL. A 1 nm-thick LiF layer was then deposited on the Alq3 layer. The first device was then fabricated by depositing a 100 nm-thick Al cathode on the LiF layer, while the second device deposited a C ₆₀ adhesion promoting layer (about 3 nm) on the LiF layer, followed by about It was prepared by depositing a magnesium cathode with a thickness greater than 3 microns.

Note that the deposition of the magnesium cathode was performed at a rate of about 30 nm/s or less. Such speeds are difficult to achieve when using the aluminum deposition technique to deposit aluminum on organic surfaces due to the need for complex and expensive devices. Moreover, damage to the substrate may be imparted by the deposited aluminum, at least in part due to the large heat formation at the surface of the organic layer. The formation of heat as described above may affect the organic layer, and finally, a device that exhibits poor performance or a device that is not functional may be derived. As above, typical aluminum deposition techniques known in the art deposit from a few atomic layers per second to several nanometers per second. Moreover, the fabrication of such devices is compared to similar devices comprising aluminum cathodes, especially when depositing a relatively thick magnesium coating layer to act as both a cathode and a getter, with or without dispersion of fullerenes. It can be completed in fewer steps.

It is well known that dark spots are generally formed in OLED devices over time due to deterioration of luminescent materials. It is also known that the rate of deterioration of a device is generally accelerated when the device is exposed to oxygen and/or water vapor. As described above, the rate of formation of dark spots in OLED devices is generally correlated with the shelf life of such devices. To represent accelerated shelf life data, the exemplary device is not packaged, and as above, the rate at which oxygen, water vapor and other species that reduce the shelf life of the OLED device can penetrate the device is It is noted that the device is larger than the case without packaging. As above, the examples provided herein are expected to exhibit substantially longer effective shelf life when packaged and substantially sealed from ambient conditions.

Returning to Figure 23A, a micrograph of an exemplary device comprising an aluminum cathode immediately after manufacturing is shown. As is evident from the micrographs above, there are few visible dark spots, but none have a significant diameter. 23B shows the same exemplary device after exposure to ambient conditions for 208 hours. 23B, there are a number of dark spots of considerable diameter. For reference, the dimensions of each of FIGS. 23A and 23B are 2 mm in height and 4.5 mm in width.

Referring to FIG. 24A, a micrograph of an exemplary device comprising magnesium cathode immediately after manufacture is shown. As can be seen from the micrograph, there are very few visible dark spots, if any. 24B shows the same exemplary device after exposure to ambient conditions for 208 hours. As shown in Figure 24B, there are only a few dark visible dark spots and the diameter of these dark spots is substantially smaller than when formed in a device comprising the aluminum cathode. The dimensions of each of FIGS. 24A and 24B are also 2 mm high and 4.5 mm wide.

Returning to Figure 25, a chart is provided plotting the total area of dark spots as a percentage of the luminescent area for the devices. As shown in Figure 25, it was observed that the device comprising the magnesium cathode deteriorated at a substantially slower rate than the same device comprising the aluminum cathode. As above, similar OLED devices comprising magnesium cathodes are expected to provide substantially longer shelf life compared to the same devices comprising conventional aluminum cathodes, especially when properly encapsulated.

Although the present invention has been disclosed with reference to several specific embodiments, various modifications thereof will be apparent to those skilled in the art. Any examples provided herein are included only for the purpose of illustrating the invention and are not intended to limit the invention in any way. Any drawings provided herein are for illustration only of various aspects of the present invention and are not intended to scale or limit the present invention in any way. The scope of the claims appended hereto should not be limited by the preferred embodiments described herein, but should provide the broadest description consistent with the specification as a whole. All prior art specifications cited in the present invention are incorporated herein by reference in their entirety.

Claims (32)

As a method of depositing a conductive coating layer on the surface,
-Treating the surface by depositing fullerene on the surface to produce a treated surface;
-Depositing the conductive coating layer on the treated surface
Including, wherein the conductive coating layer comprises magnesium and fullerene dispersed in magnesium. According to claim 1,
A method of treating said surface by depositing at least 0.1 monolayers of fullerene on the surface. According to claim 2,
A method of treating said surface by depositing at least one fullerene on the surface. According to claim 1,
How the surface is an organic surface. According to claim 1,
How the surface is a semiconductor surface or a glass surface. According to claim 1,
A method of depositing at least one of a fullerene and a conductive coating layer using an evaporation process. delete According to claim 1,
A method of depositing a fullerene and a conductive coating layer by evaporating a common source material, wherein the common source material comprises fullerene and magnesium. According to claim 1,
How to treat only part of the surface with fullerene. According to claim 1,
A method of treating a surface by depositing fullerenes using a shadow mask process or a microcontact transfer printing process. According to claim 1,
How fullerenes include one or more of C ₆₀ , C ₇₀ , C ₇₆ , C ₈₄ , single-walled carbon nanotubes and multi-walled carbon nanotubes. According to claim 1,
A method also comprising depositing a getterer on the conductive coating layer, wherein the getter comprises magnesium. According to claim 1,
A method of depositing a conductive coating layer at a rate of 1 nm or more per second. According to claim 1,
A method of depositing a conductive coating layer at a rate of 14 nm or more per second. -A substrate having a surface coated with a conductive coating layer; And
-Fullerene disposed at the interface between the conductive coating layer and the surface
It includes,
The conductive coating layer comprises magnesium and fullerene dispersed in magnesium. The method of claim 15,
A product whose surface is an organic surface. The method of claim 15,
Products whose surfaces are semiconductor surfaces or glass surfaces. The method according to any one of claims 15 to 17,
The product in which the conductive coating layer contains a magnesium alloy. delete The method of claim 15,
A product in which the conductive coating layer contains 10% by weight or less of fullerene. The method according to any one of claims 15 to 17,
Product in which the conductive coating layer comprises pure magnesium. The method of claim 15,
A product in which fullerene comprises one or more of C ₆₀ , C ₇₀ , C ₇₆ , C ₈₄ , single-walled carbon nanotubes and multi-walled carbon nanotubes. -Anode and cathode;
-An organic semiconductor layer interposed between the anode and the cathode; And
-Fullerene disposed between the organic semiconductor layer and the cathode
It includes,
The cathode comprises magnesium and fullerene dispersed in magnesium, an organic optoelectronic device. The method of claim 23,
An organic optoelectronic device that is an organic photovoltaic cell. The method of claim 23,
An organic optoelectronic device that is an organic light emitting diode. The method according to any one of claims 23 to 25,
An organic optoelectronic device in which the organic semiconductor layer comprises an electroluminescent layer. delete delete delete A common source material for use with the method of claim 8, including fullerene and magnesium. The method of claim 30,
Common source material that is solid. The method of claim 31,
A common source material that is a pellet, grain, powder, or rod, or any combination thereof.

Images